1 . Field of the Disclosure
The following is directed to bonded abrasives and particularly bonded abrasive articles incorporating microcrystalline alumina abrasive grains.
2 . Description of the Related Art
Abrasive tools are generally formed to have abrasive grains contained within a bond material for material removal applications. Superabrasive grains (e.g., diamond or cubic boron nitride (CBN)) or seeded (or even unseeded) sintered sol gel alumina abrasive grain, also referred to microcrystalline alpha-alumina (MCA) abrasive grain, can be employed in such abrasive tools and are known to provide superior grinding performance on a variety of materials. The bond material can be organic materials, such as a resin, or an inorganic material, such as a glass or vitrified material. In particular, bonded abrasive tools using a vitrified bond material and containing MCA grains or superabrasive grain are commercially useful for grinding precision metal parts and other industrial components requiring consistent and improved grinding performance.
Certain bonded abrasive tools, particularly those utilizing a vitrified bond material, require high temperature forming processes, which can have deleterious effects on the abrasive grains. In fact, it has been recognized that at such elevated temperatures necessary to form the abrasive tool, the bond material can react with the abrasive grains, particularly MCA grains, damaging the integrity of the abrasive, reducing the grain sharpness and performance properties. As a result, the industry has migrated toward reducing the formation temperatures necessary to form the bond material in order to curb the high temperature degradation of the abrasive grains during the forming process.
For example, to reduce the amount of reaction between MCA grain and vitrified bond, U.S. Pat. No. 4,543,107 discloses a bond composition suitable for firing at a temperature as low as about 900° C. In an alternate approach, U.S. Pat. No. 4,898,597 discloses a bond composition comprising at least 40% fritted materials suitable for firing at a temperature as low as about 900° C. Other such bonded abrasive articles utilizing bond materials capable of forming at temperatures below 1100° C., and in fact, below 1000° C., include U.S. Pat. Nos. 5,203,886, 5,401,284, 5,536,283, and 6,702,867. Still, the industry continues to demand improved performance of such bonded abrasive articles.